1. Field of the Invention
The present invention relates to a surface light source device used as a backlight of a liquid crystal display device or the like. In particular, the invention relates to an edge-light-type surface light source device in which a linear light source is disposed along one end face of a light guide plate.
2. Description of the Related Art
The configuration of a conventional edge-light-type surface light source device 100 will be described below with reference to FIGS. 5(a) and 5(b). Each linear light source 1 is held, at both its ends, by a holding member 2 made of a resin or rubber and is disposed along one of two end faces 3c and 3d of a light guide plate 3 that is made of an acrylic resin or the like. A lamp reflector 4 that is a metal plate or the like surrounds the associated linear light source 1 and is fitted with an end portion of the light guide plate 3. Opposed to the end face 3c or 3d, the lamp reflector 4 reflects light coming from the linear light source 1 toward the end face 3c or 3d of the light guide plate 3. An optical sheet 5 including a diffusion sheet and a lens sheet is disposed on the light emission surface 3a side of the light guide plate 3, and a reflection sheet 6 is disposed on the reflection surface 3b side of the light guide plate 3. All of the above components are held between a picture-frame-like first frame 7 that covers the periphery of the light emission surface 3a of the light guide plate 3 and partially surrounds each lamp reflector 4 and a second frame 8 that is disposed on the reflection surface 3b side of the light guide plate 3.
JP-A-5-257142 (page 12 and FIG. 36) discloses a surface light source device (i.e., a backlight of a liquid crystal display device) having a structure that a bottom case of the backlight and a reflection plate are an integral member formed by molding a white rigid resin capable of reflecting light efficiently.
Requiring the individual components such as the first frame 7, the second frame 8, and the lamp reflectors 4 and the reflection sheet 6 for reflecting light beams coming from the linear light sources 1 toward the end faces of the light guide plate 3, the conventional surface light source device of FIG. 5 has a number of components and is complex in structure. As such, the conventional surface light source device of FIG. 5 has problems that it requires complicated assembling work and the manufacturing cost is high.
To solve the above problems, the backlight disclosed in JP-A-5-257142 is a back-surface-direct-incidence-type backlight in which light beams coming from a plurality of linear light sources are reflected so as to reach a liquid crystal display portion directly. This backlight is hence different in structure from the edge-light-type backlight of FIG. 5 having such components as the light guide plate 3 and the lamp reflectors 4.